Potential phototoxicity of rosuvastatin mediated by its dihydrophenanthrene-like photoproduct

Photostability and Antiproliferative Activity of Furan Analogues of Combretastatin A-4

Cancer is one of the most serious health problems that usually require heavy medical treatment. It is important to ensure that no additional burden is placed on patients due to the modes of administration and/or poor quality of pharmaceuticals. In this regard, understanding, quantifying, and improving the photostability (resistance to UV light or sunlight) of drugs is among the important elements that can improve the patient's quality of life. In this work, the photochemical properties of a wide range of furanone analogues of combretastatin A-4 and their antiproliferative activity against A-431 epidermoid carcinoma cells were studied in a search for compounds with improved photostability and antiproliferative activity. It was found that the incorporation of an arylidene moiety led to a significant improvement in photostability, while the antiproliferative activity strongly depends on the nature of the aryl residue in the arylidene moiety. The high photostability of arylidenes was achieved due to the delocalization of the central double bond of the 1,3,5-hexatriene system, which limited the 6π-electrocyclization. The best results in terms of antiproliferative activity were obtained for thiophene arylidene (IC₅₀ = 0.6 μM) and 3,4-diarylfuran (IC₅₀ = 0.047 μM). The obtained results address the lack of data available now in scientific literature on the photodegradation of combretastatin A-4 analogues and should be taken into account in studies of the side effects of pharmaceuticals based on them.

Statin Use and Skin Cancer Risk: A Prospective Cohort Study

Epidemiological studies on statin use in relation to skin cancer risk are scarce and yielded conflicting results. We explored this association in Etude Epidémiologique auprès de femmes de l'Education Nationale, a prospective cohort of French women born in 1925-1950. Health and lifestyle data were self-reported biennially and matched with drug reimbursement data, allowing the identification of participants' statin use since 2004. Multivariable cause-specific hazards regression models adjusted for skin cancer risk factors estimated hazard ratios with 95% confidence intervals. Over 2004-2014, 455 cutaneous melanoma, 1,741 basal cell carcinoma, and 268 squamous cell carcinoma cases were ascertained among 62,473 women. Compared with never use, there were no associations between ever use of statins and melanoma (hazard ratio = 1.16, 95% confidence interval = 0.94-1.44) or squamous cell carcinoma (hazard ratio = 0.89, 95% confidence interval = 0.66-1.19) risks and a decrease in basal cell carcinoma risk with ever use of statins (hazard ratio = 0.89, 95% confidence interval = 0.79-0.996). We found no trend of increasing or decreasing risks with dose, duration of use, time since first use, or age at first use and no statistically significant effect modification by pigmentary traits or residential UVR exposure. Because of the limited number of studies evaluating the associations between the use of statins and the risks of melanoma, basal cell carcinoma, and squamous cell carcinoma, these findings would deserve further investigation in other settings.

Computational studies on statins photoactivity

Statins are popular drugs widely prescribed to control hypercholesterolaemia and to prevent cardiovascular diseases. Synthetic statins constitute a group of pharmaceuticals which are very sensitive to exposure to light in both UVA and UVB ranges. Light, by causing drugs degradation, can essentially change their pharmaceutical properties leading even to the loss of therapeutic activity and/or to the formation of deleterious photoproducts. Drugs which exhibit photochemical reactivity may elicit undesired adverse effects. A detailed understanding of mechanisms involved in molecular basis of these effects origin is very important for evaluating the photobiological risk associated with therapy in which drugs prone to exposure to light are involved. In this work we critically discussed finding regarding the mechanisms of synthetic statins phototransformation. We showed inconsistency of some previously reported facts and revised earlier presented studies. We also completed the lack of information on pitavastatin photobehaviour. This all together resulted in proposal of new schemes for the statins photodecomposition. We reviewed data derived from both experimental and computational methods. Studies of photochemical problems by the use of theoretical methods enable getting insight into areas of some fascinating events that experimental techniques can touch only indirectly. Besides effect of light, phenomenon of statins’ sensitivity to pH and resulting implications were discussed. Statins undergo pH-dependent interconversion between their pharmacologically active hydroxy acid and inactive lactone forms, and it was shown that for both forms, drugs’ interactions should be considered. Knowledge of the statins interconversion mechanisms is important for understanding how differences in the structures of their molecules can affect the drugs’ activity.

Experimental and theoretical studies on fluvastatin primary photoproduct formation

Fluvastatin (FLV) belongs to the group of compounds referred to as statins, also known as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Statins act as cholesterol-lowering agents and are among the most frequently prescribed drugs. They upregulate low-density lipoprotein receptors in the liver by binding to the active site of HMG-CoA reductase, which is the key enzyme in cholesterol biosynthesis. Statins have been detected as contaminants in natural waters and are susceptible to degradation upon exposure to light. Fluvastatin is extremely sensitive to light; upon irradiation it forms a range of photoproducts. In this study the fluvastatin molar absorption coefficient and the quantum yield of the drug photodegradation were determined. The FLV photodegradation quantum yield value determined in this work (Φ = 0.13 ± 0.02) was found to be significantly larger than that previously reported in the literature. Our results also showed that the generation of singlet oxygen is not involved in the drug photodecomposition indicating that the excited triplet state of fluvastatin is not populated efficiently. Moreover, experimental methods and DFT calculations were applied to get insight into the possible mechanisms of fluvastatin primary photoproduct formation. Using the transient absorption spectroscopy technique, the transient species formed immediately after the drug excitation were followed, and the scheme for fluvastatin primary photochemistry was suggested. The primary photoproducts were identified on the basis of spectroscopic and spectrometric methods. A new mechanism for photooxygenation leading to the formation of one of the identified photoproducts (FP2) was proposed and a new approach to the formation of the other photoproduct (FP1) was provided. The theoretical mechanistic explanation of the photoproduct formation is in excellent agreement with the experimental data.

Relation of statin use with non-melanoma skin cancer: prospective results from the Women's Health Initiative

BACKGROUND

The relationship between statin use and non-melanoma skin cancer (NMSC) is unclear with conflicting findings in literature. Data from the Women's Health Initiative (WHI) Observational Study and WHI Clinical Trial were used to investigate the prospective relationship between statin use and NMSC in non-Hispanic white (NHW) postmenopausal women.

METHODS

The WHI study enrolled women aged 50-79 years at 40 US centres. Among 133,541 NHW participants, 118,357 with no cancer history at baseline and complete medication/covariate data comprised the analytic cohort. The association of statin use (baseline, overall as a time-varying variable, duration, type, potency, lipophilicity) and NMSC incidence was determined using random-effects logistic regression models.

RESULTS

Over a mean of 10.5 years of follow-up, we identified 11,555 NMSC cases. Compared with participants with no statin use, use of any statin at baseline was associated with significantly increased NMSC incidence (adjusted odds ratio (ORadj) 1.21; 95% confidence interval (CI): 1.07-1.35)). In particular, lovastatin (OR 1.52; 95% CI: 1.08-2.16), simvastatin (OR 1.38; 95% CI: 1.12-1.69), and lipophilic statins (OR 1.39; 95% CI: 1.18-1.64) were associated with higher NMSC risk. Low and high, but not medium, potency statins were associated with higher NMSC risk. No significant effect modification of the statin-NMSC relationship was found for age, BMI, smoking, solar irradiation, vitamin D use, and skin cancer history.

CONCLUSIONS

Use of statins, particularly lipophilic statins, was associated with increased NMSC risk in postmenopausal white women in the WHI cohort. The lack of duration-effect relationship points to possible residual confounding. Additional prospective research should further investigate this relationship.

Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer

For many biological and biomedical studies, it is essential to detect the production of (1)O2 and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6-tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been widely employed, it can produce misleading data. This is demonstrated by the present study, in which the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method are compared for a set of well-known photosensitizers. The results reveal that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizer is efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP(+) radical cation, followed by deprotonation and reaction with molecular oxygen, gives rise to an EPR-detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological, and medical studies.